Support for Cassandra Channel

[vpatil-tibco]

Context

Adding support for Cassandra channel. The goal of this channel is to have a behavior similar to that of AS Channel, where we track Table changes i.e. insert/delete/expire, filtering if available.

Alternatives

None
Has the feature been requested before?

Yes, by FedEx, they are moving from AS to Cassandra and are looking for alternatives to AS Channel. SR - https://supportapps.na.tibco.com/query?q=02139348&s=ka&p=kwbe

If the feature request is approved, would you be willing to submit a PR?

Yes

[vpatil-tibco]

Take a look at these links,
https://issues.apache.org/jira/browse/CASSANDRA-8844
https://github.com/apache/cassandra/blob/8b3a60b9a7dbefeecc06bace617279612ec7092d/doc/source/operating/cdc.rst

So it seems to write the commit log to a file and then you can read off the file to identify the changes. They also have a file CommitLogReader, which can be used to read this log.

[rakulkar-tibco]

v99855 -Pulsar channel changes in order to support Cassandra as a channel.

[rakulkar-tibco]

@vilasshelar QA can start testing this feature. Related required changes are also checked-in inside pulsar channel in trunk.